- "Friendship may be thus defined: a complete accord on all subjects human and divine, joined with mutual goodwill and affection."

- "What can be more delightful than to have some one to whom you can say everything with the same absolute confidence as to yourself?"

- "In the face of a true friend a man sees as it were a second self."

- "If it were true that its material advantages cemented friendship, it would be equally true that any change in them would dissolve it."

- "While the most fatal blow to friendship in the majority of cases was the lust of gold, in the case of the best men it was a rivalry for office and reputation, by which it had often happened that the most violent enmity had arisen between the closest friends."

- "The plea of having acted in the interests of a friend is not a valid excuse for a wrong action. (...) We may then lay down this rule of friendship - neither ask nor consent to do what is wrong."

- "If you take away emotion, what difference remains I don't say between a man and a beast, but between a man and a stone or a log of wood, or anything else of that kind?"

- "The true rule is to take such care in the selection of our friends as never to enter upon a friendship with a man whom we could under any circumstances come to hate. And even if we are unlucky in our choice, we must put up with it—according to Scipio—in preference to making calculations as to a future breach."

- "The real limit to be observed in friendship is this: the characters of two friends must be stainless. There must be complete harmony of interests, purpose, and aims, without exception."

- "He must neither take pleasure in bringing accusations against us himself, nor believe them when they are brought."

- "First, he will be entirely without any make-believe or pretence of feeling; for the open display even of dislike is more becoming to an ingenuous character than a studied concealment of sentiment. Secondly, he will not only reject all accusations brought against his friend by another, but he will not be suspicious himself either, nor be always thinking that his friend has acted improperly."

- "Here is another golden rule in friendship: put yourself on a level with your friend."

- "People must not, for instance, regard as fast friends all whom in their youthful enthusiasm for hunting or football they liked for having the same tastes."

- "Another good rule in friendship is this: do not let an excessive affection hinder the highest interests of your friends. (...) There are, of course, limits to what you ought to expect from a friend and to what you should allow him to demand of you. And these you must take into calculation in every case."

- "There can be nothing more discreditable than to be at open war with a man with whom you have been intimate."

- "Our first object, then, should be to prevent a breach; our second, to secure that, if it does occur, our friendship should seem to have died a natural rather than a violent death. Next, we should take care that friendship is not converted into active hostility, from which flow personal quarrels, abusive language, and angry recriminations."

- "Most people unreasonably, not to speak of modesty, want such a friend as they are unable to be themselves, and expect from their friends what they do not themselves give."

- "If a man could ascend to heaven and get a clear view of the natural order of the universe, and the beauty of the heavenly bodies, that wonderful spectacle would give him small pleasure, though nothing could be conceived more delightful if he had but had some one to whom to tell what he had seen."

- "My friend Terence says in his Andria: Compliance gets us friends, plain speaking hate. (...) Plain speaking is a cause of trouble, if the result of it is resentment, which is poison of friendship; but compliance is really the cause of much more trouble, because by indulging his faults it lets a friend plunge into headlong ruin."

- "There are people who owe more to bitter enemies than to apparently pleasant friends: the former often speak the truth, the latter never."